Background Many athletes have foot deformity of hallux-valgus. These deformities lead to decrease of foot function and sports performance. The authors were developed a new device for decrease the angle of hallux-valgus. This device was socks and in use underwear in sports activity and daily living.

Objective The purpose of this study was following four points. Does this device can change the hallux-valgus angle? Does this device can change the foot pain? Does this device influence centre of pressure (COP) of the foot? Does this device can decrease the deformity for long-term use?

Design Prospective and randomised controlled trial design.

Setting This study was clinical setting for athletes.

Participants The subjects were 34 female volunteer athletes. The hallux-valgus group was consisted 17 athletes, all who has hallux-valgus angle above 20° and complaint of foot pain. The control group was 17, all who has hallux-valgus angle below 19° and pain free of each foot.

Intervention The subjects were used this socks 3 months of their daily life and sports activities.

Main outcome measurements The hallux-valgus angle and COP of standing position were measured, and checked again after the 3 months.

Results The hallux-valgus angle was decreased 7.1° at instance of wearing the socks with hallux-valgus group and 5.5° with control group. The foot pain was decreased 50% at instance of wearing socks with hallux-valgus group and 70% decrease at 2.3 months uses the socks. The COP of the body was changed 3.7% forward on the foot of hallux-valgus group. The 2.3 months later, hallux-valgus angle was decreased 4.7° of average at the bare foot with hallux-valgus group.

Conclusions This study showed the hallux-valgus prevention socks were decreased not only deformity angle at instance but also use prolonged more angle decreased.